1. Field of the Invention
This invention relates to methods of lining pipes, and to pipes so lined, exposed to corrosive environments particularly to cement liners for metal pipe that carry corrosive fluids.
2. State of the Art
Cement is used to line pipes that are conduits for corrosive or otherwise hard to handle compositions. One class of such corrosive compositions that must be transported through pipes is geothermal brines and steam used to extract power from the earth. Although the cement used to line such pipes can be standard Portland cement used without any special additives, many special cements are used for this purpose. For example, U.S. Pat. No. 5,122,554, said patent incorporated by reference in full herein, describes enhanced polymer concrete compositions. Polymer cements have the disadvantage of being more costly to produce than cements hydrated with water (i.e., hydraulic cements). However, water hydrated cements are subject to cracking caused by dry shrinkage during manufacture and storage, mechanical jarring during fabrication into pipelines, and corrosion and erosion during use as pipelines. The cracks propagate until they penetrate through the cement liner and allow the corrosive contents of the pipe to contact the metal shell of the pipe, which, in turn, causes metal corrosion and the eventual failure of the pipe.
It would be advantageous to have a liner that was less costly to produce and did not crack or otherwise expose the supporting metal of the pipe to the corrosive contents of the pipeline.